Fuel oil with improved low temperature flowability

ABSTRACT

THE RESPONSE OF A MIDDLE DISTILLATE FUEL OIL, BOILING WITHIN THE RANGE OF ABOUT 250* TO ABOUT 670*F. AND CONTAINING PARAFFINIC CONSTITUENTS, TO THE ADDITION OF A FLOWIMPROVING ADDITIVE SUCH AS A COPOLYMER OF EHTHYLENE IS IMPROVED BY ADDING TO THE FUEL OIL FROM ABOUT 1 TO ABOUT 12 WEIGHT PERCENT OF A CATALYTIC RECYCLE OIL OBTAINED FROM THE CATALYTIC CRACKING OF A PETROLEUM FRACTION, SAID RECYCLE OIL BEING A RELATIVELY HIGH BOILING FRACTION HAVING A 50 PERCENT ATMOSPHERIC DISTILLATION POINT WITHIN THE RANGE OF ABOUT 660* TO ABOUT 740*F. AND HAVING A FINAL BOILING POINT WITHIN THE RANGE OF ABOUT 775* TO ABOUT 975*F.

United States Patent 3,832,150 FUEL OIL WITH IMPROVED LOW TEMPERATURE FLOWABILITY Nicholas Feldman, Woodbridge, N.J., assignor to Esso Research and Engineering Company No Drawing. Continuation-impart of abandoned application Ser. No. 760,359, Sept. 17, 1968. This application Oct. 27, 1971, Ser. No. 193,156

Int. Cl. C101 1/22 US. C]. 44-62 7 Claims ABSTRACT OF THE DISCLOSURE The response of a middle distillate fuel oil, boiling within the range of about 250 to about 670 F. and con taining parafiinic constituents, to the addition of a flowimproving additive such as a copolymer of ethylene is improved by adding to the fuel oil from about 1 to about 12 weight percent of a catalytic recycle oil obtained from the catalytic cracking of a petroleum fraction, said recycle oil being a relatively high boiling fraction having a 50 percent atmospheric distillation point within the range of about 660 to about 740 F. and having a final boiling point within the range of about 775 to about 975 F.

REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of copending application Ser. No. 760,359, filed Sept. 17, 1968 now abandoned.

FIELD OF THE INVENTION This invention concerns an improvement in the low temperature flowability of a middle distillate petroleum fuel wherein there is utilized a copolymer pour point depressant or flow improver of the type comprising a copolymer of ethylene with another ethylenically unsaturated monomer, such as an unsaturated ester or another olefin, wherein the ethylene forms a backbone along which there are randomly distributed side chains consisting of hydrocarbon groups or of oxy-substituted hydrocarbon groups of up to 16 carbon atoms. It has been found in accordance with this invention that the response of a middle distillate fuel oil to the addition of a flow improver of the types mentioned will be greatly improved if there is added to the fuel oil a small percentage of a relatively high boiling catalytic recycle oil.

DESCRIPTION OF THE PRIOR ART The use of copolymers of ethylene and other polar monomers such as vinyl esters, acrylate or methacrylate esters, and the like to lower the pour point and improve the fiowability of middle distillate fuels at low temperatures is well known in the art. See for example US. Pats. 3,037,850, 3,048,079, 3,069,245, 3,093,623 and 3,236,612.

DESCRIPTION OF THE INVENTION Heating oils and other middle distillate petroleum fuels, e.g. Diesel fuels, contain small amounts of hydrocarbon waxes which tend to precipitate in large interlocking crystals at low temperatures. These hydrocarbon waxes are largely normal parafiins. This interlocking of the crystals sets up a gel structure which causes the fuel to lose its fluidity. The lowest temperature at which the oil will flow is known as pour point. When the fuel temperature reaches or goes below the pour point and the fuel is no longer freely fiowable, difliculty arises in transporting the fuel through flow lines and pumps, as for example when attempting to transfer the fuel from one storage vessel to another by gravity or under pump pressure or when attempting to feed the fuel to a burner. Additionally, the wax crystals that have come out of solution tend to plug fuel lines, screens, and filters. This problem has been well recognized in the past and various additives have been suggested for depressing the pour point of the fuel oil. One function of such pour point depressants has been to change the form or size of the crystals that precipitate from the fuel oil. While reduction of pour point per se is important, the size and shape of the wax particles formed at low temperatures are also very important. Thus, even though a pour point depressant may function to lower the temperature at which the oil will no longer flow, wax crystallization can still occur at a point above the pour point, i.e. at the cloud point, which is the point at which the oil becomes cloudy because of wax crystallization. Small size crystals are desirable so that the precipitated wax will not clog the fine mesh screens that are provided in fuel transportation, storage, and dispensing equipment. Pour point depressants that function by changing the wax crystals to a more advantageous size and shape can thus also be referred to as flow improvers. It is desirable to obtain not only fuel oils with low pour points but also oils that will form small wax crystals so that the clogging of filters will not impair the flow of the fuel at low operating temperatures. At the same time it is desirable to employ the minimum amount of pour point depressant that is necessary to obtain these desired results in order to minimize cost.

In accordance with the present invention it is found that the amount of a pour point depressant or flow improver, particularly of the type comprising a copolymer of ethylene and another unsaturated monomer, that is necessary in order to obtain the required improvement in low temperature fiow properties of the fuel oil can be minimized by adding to the fuel oil from about 1 to about 10 weight percent of the recycle oil will be used.

Catalytic recycle oil is obtained as one of the products in the catalytic cracking process that is used for converting higher boiling portions of a petroleum crude oil into lower boiling commercially valuable products, including gasoline and heating oils. conventionally, the feedstock to a catalytic cracking unit is a portion of a petroleum crude oil boiling above the gasoline range, e.g., a gas oil or other petroleum fraction boiling within the range of about 430 F. and about 1100 F. The catalytic cracking operation may be of the fixed bed type, moving bed type, or fluidized bed type, using any of the various well-known cracking catalysts. Generally, such catalysts are of the metal oxide type and preferably include silica alumina, silicamagnesia, or silica gel promoted with metal oxides which are adsorbed thereon. Typical cracking conditions include temperatures in the range of about 750 to 1050 F, and pressures ranging from atmospheric to somewhat above atmospheric pressure. The catalytic agent employed is regenerated intermittently or continuously in order to restore or maintain the activity of the catalyst.

In the nomenclature of the petroleum art it is common practice to refer to any product of a catalytic cracking operation above the gasoline range as cycle stock or cycle oil. (See US. Pat. 2,859,172, column 4, line 6.) In modern day refining, one side stream of the product fractionator is cut at about 430 F. end point and used in gasoline blending, and a second side stream boiling from a cut point of about 430 F. to a cut point of about 650 F. to 670 F. is taken for use as a component of fuel oils or heating oils. This side stream is commonly referred to in the art as light cycle oil, cycle gas oil, cracked gas oil, and the like. A still higher boiling stream boiling in the range of an initial cut point of about 650 F. to a final cut point somewhere in the region of about 775 F. to about 975 F. is also taken from the fractionator and recycled to the catalytic cracking zone. This fraction is known as catalytic recycle oil, and it is this fraction, which has not heretofore been employed as a component of a petroleum distillate fuel oil, that is used in small proportions to improve the response of the petroleum distillate fuel to a flow improver of the type described.

It is to be recognized that a fraction cut from a fractionator starting at about 650 F. will, when again distilled separately, be found to have some components that boil below 650 F., because of the nature of the original fractional distillation range within the limits of about 550 F. and about 975 F. More usually the recycle oil will have a boiling range at atmospheric pressure within the limits of about 575 F. and about 900 F., with a 5% distillation point in excess of 600 F., and a final boiling point of from about 850 F. to about 900 F.

The catalytic recycle oil is best defined as having a mid-boiling point, i.e., a 50% distillation point, at atmospheric pressure, somewhere between about 660 F. and 740 F., e.g., a mid-boiling point of 680 or 690 F. Atmospheric distillation ranges can be calculated from vacuum distillation data mm. Hg pressure; ASTM D-ll60) by the use of conventional vapor pressure charts, as is well known in the art.

This catalytic recycle oil will contain a large proportion of cyclic hydrocarbons and a small percentage of normal paraffinic hydrocarbons ranging up to about 30 carbon atoms. It is believed that it is the presence of the paraffinic hydrocarbons of from 24 carbon atoms and higher that serves to improve the response of the fuel oil.

The distillate fuel oils that can be improved by the practice of this invention include those that have atmospheric boiling ranges within the limits of about 250 F. to about 670 F. In present commercial practice, most distillate fuel oils have a final atmospheric boiling point of about 630 F. to 640 F., and a mid-boiling point (50% distillation point) of about 500 F. to 520 F. Most distillate fuel oils are prepared by blending straight-run or virgin stocks with thermally and/or catalytically cracked petroleum fractions.

The most common petroleum middle distillate fuels are kerosene, diesel fuels, jet fuels and heating oils. Since jet fuels are normally refined to very low pour points there will be generally no need to apply the present invention to such fuels. The low temperature flow problem may arise occasionally with kerosene but it is most usually encountered with diesel fuel and with Number 2 heating oils. The specifications for a representative kerosene include a 10% ASTM distillation point of about 400 F. to 420 F, a 90% distillation point of about 500 F., and a final boiling point of about 530 F. A representative Number 2 heating oil specification calls for a 10% distillation point no higher than about 440 F., a 50% point no higher than about 520 'F., and a 90% point of at least 540 F. and no higher than about 640 F. to 650 F. Heating oils are preferably made of a blend of virgin distillate, e.g., gas oil, naphtha, etc., and cracked distillates, e.g., catalytic cycle tock.

The pour point depressants or flow improvers that are employed in this invention are of the type comprising a copolymer of ethylene and at least one second unsaturated monomer. The second unsaturated monomer can be another monoolefin, e.g., a C to C alpha-monoolefin, or it can be an unsaturated ester, as for example vinyl acetate, vinyl butyrate, vinyl propionate, lauryl methacrylate, ethyl acrylate or the like.(.See Canadian Pats. 676,875 and 695,679.) Other monomers include N-vinyl pyrrolidone. (See Canadian Pat. 658,216.) The second monomer can also be a mixture of an unsaturated mono or diester and a branched or straight chain alpha monoolefin. Mixtures of copolymers can also be used, as for example a mixture of a copolymer of ethylene and vinyl acetate with an alkylated polystyrene or acylated polystyrene. (See U.S. Patents 3,037,850 and 3,069,245.)

Stated more generally, a copolymer pour depressant useful in this invention will consist essentially of about 3 to 40, and preferably 3 to 20, molar proportions of ethylene per molar proportion of the ethylenically unsaturated monomer, which latter monomer can be a single monomer or a mixture of such monomers in any proportion, said polymer being oil-soluble and having a number average molecular weight in the range of about 1,000 to 50,000, preferably about 1,500 to about 5,000 molecular weight. Molecular weights can be measured by vapor phase osmometry, for example by using a Mechrolab Vapor Phase Osmometer Model 310A.

The unsaturated monomers, copolymerizable with ethylene, include unsaturated acids, acid anhydrides, and monoand diesters of the general formula:

wherein R is hydrogen or methyl; R is a OOCR or -C0O'R group wherein R is hydrogen or a C to C more usually a C to C straight or branched chain alkyl group and R3 is hydrogen or -COOR The monomer, when R to R are hydrogen and R is OOCR includes vinyl alcohol esters of C to C monocarboxylic acids. Examples of such esters include vinyl acetate, vinyl isobutyrate, vinyl laurate, vinyl myristate, vinyl palmitate, etc. When R is -COOR such esters include C Oxo alcohol acrylate, methyl acrylate, methyl methacrylate, lauryl acrylate, isobutyl methacrylate, palmityl alcohol ester of alpha-methyl-acrylic acid, C Oxo alcohol esters of methacrylic acid, etc. Examples of monomers wherein R is hydrogen and R and R are OOCR groups, include mono-C Oxo alcohol fumarate, di-C Oxo alcohol fumarate, diisopropyl maleate; dilauryl fumarate; ethyl methyl fumarate, fumaric acid, maleic acid, etc.

Other unsaturated monomers copolymerizable with ethylene to prepare pour point depressants or flow improvers useful in this invention include C to C branched chain or straight-chain alpha monoolefins, as for example propylene, n-octene-l, 2-ethyl clecene-l, n-decene-l, etc.

Small proportions, e.g., about 0 to 20 mole percent, of a third monomer, or even of a fourth monomer, can also be included in the copolymers, as for example a C to C branched or straight chain alpha mono-olefin, e.g., propylene, n-octene-l, n-decene-l, etc. Thus, for example, a copolymer of 3 to 40 moles of ethylene with one mole of a mixture of 30 to 99 mole percent of unsaturated ester and 70 to 1 mole percent of olefin could be used.

The copolymers that are formed are random copolymers consisting primarily of an ethylene polymer backbone along which are distributed side chains of hydrocarbon or oxy-substituted hydrocarbon.

The Oxo alcohols used in preparing the esters mentioned above are isomeric mixtures of branched chain aliphatic primary alcohols prepared from olefins, such as polymers and copolymers of C to C monoolefins, reacted with carbon monoxide and hydrogen in the presence of a cobalt-containing catalyst such as cobalt car bonyl, at temperatures of about 300 F. to 400 F., under pressures of about 1000 to 3000 p.s.i., to form aldehydes. The resulting aldehyde product is then hydrogenated to form the 0x0 alcohol, the latter being recovered by distillation from the hydrogenated product.

Any of the known methods for polymer preparation can be used in preparing the copolymer flow improver or pour depressant, including the techniques taught for ethylene-vinyl ester polymerization in U.S. Pats. 3,048; 479, 3,131,168, 3,093,623 and 3,254,063. However, a particularly useful technique is as follows: Solvent and a portion (e.g., 5 to 50 percent of the total amount to be reacted) of each of the unsaturated monomers, that is to be copolymerized with the ethylene are charged to a stainless steel pressure vessel which is equipped With a stirrer. The temperature of the pressure vessel is then brought to reaction temperature and pressured to the desired pressure with ethylene. Then a catalyst, which can be dissolved in a solvent to aid in handling, and additional amounts of the comonomer or comonomers are added to the vessel periodically or continuously during the reaction time. Also during this reaction time, as ethylene is consumed in the polymerization, additional ethylene is supplied through a pressure controlling regulator so as to maintain the desired reaction pressure fairly constant at all times. Following the completion of the reaction, the liquid phase of the contents of the pressure vessel is distilled to remove the solvent and other volatile constituents of the reacted mixture, leaving the polymer as residue. In general, based upon 100 parts by weight of polymer to be produced, about 100 to 600 parts by weight of solvent, and about 1 to parts by weight of catalyst, will be used.

The catalyst, or promoter, will generally be of the free radical type, including organic peroxide types such as benzoyl peroxide, diacetyl peroxide, ditertiary butyl peroxide, dicumyl peroxide, tertiary butyl perbenzoate, dilauroyl peroxide, t-butyl hydroperoxide, and also such nonperoxy compounds as azo-bis-isobutyronitrile, and the like.

The solvent can be any nonreactive organic solvent for furnishing a liquid phase reaction, preferably a hydrocarbon solvent such as benzene, hexane, or the like. The solvent should, of course, be one that will not poison the catalyst or otherwise interfere with the reaction.

Temperatures and pressures employed may vary widely. For example, depending partly on the decomposition temperature of the catalyst, the temperature may range from 100 F. to 450 'F., with pressures of 500 to 30,000 p.s.i.g. However, usually the temperature will range between about 160 F. and about 350 F. Relatively moderate pressures of 700 to about 3000 p.s.i.g. will be used with vinyl esters such as vinyl acetate, whereas with esters that have a lower reactivity to ethylene, such as methyl methacrylate somewhat higher pressures, e.g., 3000 to 10,000 p.s.i.g. are more satisfactory. A superatmospheric pressure is employed which is at least sufiicient to maintain a liquid phase medium under the reaction conditions, and is sufficient to maintain the desired concentration of ethylene in solution in the solvent. In general, this pressure is attained by maintaining a continuous pressure on the reaction chamber through controlling the inlet feed of ethylene. The time of reaction will generally be within 1 to 10 hours, the reaction time being usually interrelated with the reaction temperature and pressure, and will also vary with the particular catalyst used.

The pour point depressant or flow improver is generally used in a concentration in the range of from about 0.001 to about 2 weight percent, preferably from about 0.005 to about 0.5 percent by weight, based on the weight of the fuel oil being treated.

The specific copolymer of ethylene and vinyl ester used in the working examples of the invention, and referred to as flow improver A, consisted of about 65 weight percent of ethylene and about 35 weight percent of vinyl acetate, and the copolymer had a number average molecular weight of about 2000 as measured by vapor phase os mometry. The copolymer was prepared by copolymerizing ethylene and vinyl acetate, using di-tertiary-butyl peroxide catalyst, etc. (See Belgium Pat. 673,566 and French Pat. 1,461,008.)

A typical preparation of this copolymer is as follows:

A three-liter stirred autoclave is charged with 1150 ml. of benzene as solvent and 40 ml. of vinyl acetate. The vapor space of the autoclave is then purged with a stream of nitrogen, followed by a stream of ethylene. The autoclave is then heated to about 300 F. while ethylene is pressured into the autoclave until a pressure of 950 p.s.i.g. is reached. Then, while maintaining a temperature of about 300 F. and 950 p.s.i.g. pressure, 90 ml./hour of vinyl acetate and ml./hour of a solution consisting of 23 wt. percent t-butyl peroxide dissolved in 77 wt. percent of benzene, are continuously pumped into the autoclave at an even rate. Vinyl acetate is injected over about 135 minutes, while the peroxide solution is injected into the reactor over a period of about 150 minutes from the start of the injection. After the last of the peroxide solution is injected, the batch is maintained at 300 F. for an additional 15 minutes. Then, the temperature of the reactor contents is lowered to about F., the reactor is depressured, and the contents are discharged from the autoclave. The emptied reactor is rinsed with 1 liter of warm benzene (at about 120 P.) which is added to the product. The product mixture is then stripped of the solvent and unreacted monomers by blowing nitrogen through it while it is heated on a steam bath.

Flow improver B, referred to in the examples, was prepared by the same general method as flow improver A, using ethylene, vinyl acetate, and a mixture of ot-monoolefins having a range of 12 to 16 carbon atoms. The vinyl acetate and mixed olefins were fed into the reactor together during the course of the reaction. Specifically the initial charge to the reactor was 670 ml. of benzene and 32 ml. of vinyl acetate, the reaction pressure was 900 p.s.i.g., the reaction temperature was 220 F., the catalyst was lauryl peroxide, the mixture of 80 wt. percent vinyl acetate and 20 wt. percent mixed olefins was injected at the rate of 80 ml. per hour for minutes, and the total reaction time was minutes. The yield was 255 grams of copolymer. The copolymer in 47 wt. percent solution in kerosene has a kinematic viscosity of 136 cs. at 100 F.

Flow improver C is a copolymer of 22 wt. percent vinyl acetate, 8 wt. percent C Oxo alcohol diesters of fumaric acid, and 70 wt. percent of ethylene, the copolymer having a number average molecular weight of 2400 as measured by vapor phase osmometry.

It will be understood that although the fuel oil blends tested in the following examples contain only pour depressant additives, other additives that are commonly used in distillate f-uels can also be employed, including viscosity index improvers, rust inhibitors, antiemulsifying agents, antioxidants, sludge dispersants, dyes, dye stabilizers, haze inhibitors and so forth.

The invention will be further understood when reference is made to the following examples, which include preferred embodiments.

EXAMPLE 1 Fuel oil blends were prepared using two separate middle distillate fuel oils each of which comprised a mixture of straight run and cracked components. Fuel Oil A had an atmospheric boiling range of about 296 F. to 620 F. and a cloud point of +6 F. Fuel Oil B had a boiling range of about 315 F. to 645 F. at atmospheric pressure and had a cloud point of +14 F. Various percentages of flow improver A, previously described, were added to separate portions of each of the fuels. 'Each of the fuels was modified to prepare additional blends by adding a catalytic recycle oil in a concentration in the range of about 4 to 6 wt. percent.

This catalytic recycle oil had been obtained from the product fractionator of a catalytic cracking process wherein a feedstock comprising a mixed gas oil was contacted with a fluidized bed of cracking catalyst comprising zeolite on a silica-alumina base.

The catalytic recycle oil was found to contain 64 wt. percent aromatic hydrocarbons, and 36 wt. percent of saturated hydrocarbons, of which about /3, or 14 wt. percent of the total oil, was normal paraffins ranging from C H to C H The atmospheric distillation data on the catalytic recycle oil were as follows:

The distributon of the normal parafiins in the catalytic recycle oil was as follows:

Carbon atoms: Weight percent Each of the blend mentioned above was subjected to a laboratory fluidity test that has been found to give results which correlate with field tests that have been run to measure the low temperature flowability of fuel oils. Briefly described, this test, called the Programmed Fluidity Test, consists of allowing the test oil to flow by gravity through a standard sized opening for a period of 3 minutes and then measuring the percent of the volume of oil which will flow through the opening during this period of time.

Specifically this fluidity test was carried out in the following manner. The test instrument is essentially an hour-glass-shaped device having upper and lower chambers connected by a passageway having an internal diameter of about 2.25 mm. (0.1 inch). The lower section is covered by a thin aluminum disc. The lower chamber of the instmment is filled with 40 milliliters of the fuel to be tested and then the fuel is cooled to a temperature which is F. above the predetermined cloud point of the fuel. Then the sample is cooled evenly at a rate of 4 F. per hour until a temperature of -l0 F. is reached, the latter being the temperature at which the test is run. At this time, a reading is taken of the volume of fuel in the test instrument and then the sample container is inverted. After one minute of settling time, the disc is punctured and the oil is permitted to drain through the flow opening for a period of 3 minutes. The percentage of oil that drains through the opening in this period is referred to as percent recovery. Less than 80% recovery is considered to be a failure of the test. Each test is run in quadruplicate. If the test is a failure, tests are run with additional amounts of pour point depressants or flow improver until a pass is obtained.

The test results obtained with the blends described above are given in the following Table I.

TAB LE I Percent of- Recycle Recovery oil added Additive at -l0 F.

Fuel oil A Fuel oil B In the manner of Example 1 additional blends were prepared, using in one case a heating oil having an end point of 655 F. and a cloud point of +l6 F., hereinafter referred to as Oil C and in another case an oil identified as Oil D, which was a heating oil having an end point of 605 F. and a cloud point of 0 F. Using the fluidity test described in Example 1, the amount of Flow Improver A required to pass the test both in the presence and absence of catalytic recycle oil was determined. The catalytic recycle oil was the same as used in Example 1. The results are given in Table II.

To a heating oil of 29.5 API gravity, consisting of percent catalytically cracked fuel of 654 F. final boiling point and 20 percent of heavy virgin naphtha boiling from 290 F. to 430 F. there are added 5 wt. percent of a catalytic recycle oil, having a 5% distillation point of 614 F. and a final boiling point of 863 F. and containing 14 percent of normal paraffin hydrocarbons ranging from C17H30 to C H together with 0.11 wt. percent of Flow Improver B, described above.

EXAMPLE 4 A petroleum distilled fuel comprising a blend of straight-run and cracked distillate stocks and having an initial boiling point of 310 F. and a final boiling point of 665 F. is improved in low temperature flowability by incorporating therein 6 wt. percent of the catalytic recycle oil described in Example 1 together with 0.12 Wt. percent of a copolymer of ethylene and isobutyl acrylate of 2400 number average molecular weight, the copolymer having about 7.2 ethylene units per mole of isobutyl methacrylate.

EXAMPLE 5 A heating oil of 30.3 API gravity, made up of volume percent catalytically cracked stocks of 660 F. final boiling point and 15 volume percent of heavy virgin naphtha boiling from 290 F. to 430 F. is improved in low temperature flow properties by adding thereto 7 Wt. percent of a catalytic recycle stock of 630 F. 5% distillation point and 881 F. final boiling point together with 0.12 wt. percent of flow improver C, described above, i.e., a 2400 molecular weight terpolymer of vinyl acetate, ethylene, and C Oxo alcohol diesters of fumaric acid.

EXAMPLE 6 Example 4 is repeated, substituting for the flow improver therein described 0.15 wt. percent of a copolymer of 75 wt. percent of ethylene and 25 wt. of propylene, the copolymer having a number average molecular weight of about 3200 and having been prepared by the method described in British Pat. 993,744.

In the foregoing examples, the stated Weight percent of recycle oil in each blend is on a total composition basis. Thus, for instance when it is stated (e.g., in EX- ample 2) that 10 wt. percent of recycle oil was added to Fuel Oil D, what is meant is that the resulting blend was made up of wt. percent of Fuel Oil D and 10 Wt. percent of recycle oil.

It will be understood that the foregoing examples are presented by way of illustration and not limitation, and that modifications thereof are contemplated Within the spirit and scope of the invention. The scope is defined by the appended claims.

What is claimed is:

1. A petroleum distillate fuel having a boiling range within the limits of about 250 F. and about 670 F.

which has been improved with respect to its low temperature flow properties by adding thereto from about 1 to about 12 wt. percent of a catalytic recycle oil fraction and from about 0.001 to about 2 wt. percent of an oilsoluble wax-modifying random copolymer of ethylene and at least one additional ethylenically unsaturated polymerizable monomer, said weight percents being based on the total composition; said copolymer having an average molecular weight of from about 1000 to 50,000 and comprising about 3 to 40 molar proportions of ethylene per molar proportion of other monomers, said coploymer consisting primarily of an ethylene polymer backbone along which are distributed side chains of hydrocarbon or oxysubstituted hydrocarbon, said other monomers being selected from the group consisting of an alpha monoolefin of 3 to 16 carbon atoms; N-vinyl pyrrolidone; and an unsaturated acid, unsaturated acid anhydride, unsaturated monoester, or unsaturated diester, of the general formula:

wherein R is hydrogen or methyl; R is a --OOCR 01' COOR group wherein R is hydrogen or a C to C straight or branched chain alkyl group and R is hydrogen or -COOR said recycle oil fraction containing normal paraffin hydrocarbons and having been obtained in the catalytic cracking of a petroleum oil, said recycle oil fraction having a 50% distillation point at atmospheric pressure within the range of about 66 F. and about 740 F.

2. Petroleum distillate fuel as defined by claim 1 wherein said catalytic recycle oil has a 5% distillation point in excess of 600 F. at atmospheric pressure.

3. Petroleum distillate fuel as defined in claim 1 wherein said catalytic recycle oil has a boiling range at 3 atmospheric pressure within the limits of about 550 F. and 975 F.

4. Petroleum distillate fuel as defined in claim 1 wherein said copolymer is a copolymer of ethylene and an unsaturated ester.

5. Petroleum distillate fuel as defined by claim 1 wherein said copolymer is a copolymer of ethylene and another olefin.

6. Petroleum distillate fuel as defined in claim 1 wherein said copolymer is a copolymer of ethylene and vinyl acetate.

7. Petroleum distillate fuel as defined by claim 1 wherein said copolymer is a terpolymer of ethylene, vinyl acetate and aliphatic alcohol diester of fumaric acid.

References Cited UNITED STATES PATENTS 2,379,728 7/1945 Lieber et a1. 4462 X 3,093,623 6/ 1963 Ilnyckyj 4462 X 3,236,612 2/1966 Ilnyckyj 4462 3,288,577 11/1966 Patinkin et a1. 4462 3,341,309 9/ 1967 Ilnyckyj 4462 2,664,388 12/1953 Winterhalter 208-15 X 3,338,816 8/1967 Tritsmans 208-33 X 3,689,402 9/1972 Youngblood et a1 20815 3,660,057 5/ 1972 Ilnyckyj 4470 3,660,058 5/ 1972 Feldman et a1. 4480 3,640,691 2/ 1972 Ilnyckyj et a1. 4480 FOREIGN PATENTS 993,744 6/ 1965 Great Britain 4462 DANIEL E. WYMAN, Primary Examiner Y. H. SMITH, Assistant Examiner US. Cl. X.R. 

